Technetium Tc 99m Bicisate (Systemic)

Another commonly used name for bicisate is
ethyl cysteinate dimer (ECD) .Note: For a listing of dosage forms and brand names by country availability, see Dosage Forms section(s).

Category:

Diagnostic aid, radioactive (cerebrovascular disease)—

Indications

Note: Bracketed information in the Indications section refers to uses that are not included in U.S. product labeling.Accepted

Brain imaging, radionuclide—Single-photon emission computed tomography (SPECT) {28} using technetium Tc 99m bicisate is indicated as an adjunct to conventional computed tomography (CT) or magnetic resonance imaging (MRI) in the localization of stroke in patients in whom stroke has already been diagnosed. {01}{07}{08}{09}{13}{15}{20}{21}{22}{31} However, [technetium Tc 99m bicisate is also used in the evaluation and localization of altered regional cerebral perfusion{05}{10}{12}{14}{15}{16}{17}{19}{24}{25}{27} associated with functional impairment in patients with neurological disorders not limited to stroke{29}{30} , but including such disorders as dementia{15}{29}{32}{33} , head trauma{29} , and epilepsy{29}{34}{35}] .

Brain imaging—Technetium Tc 99m bicisate is a lipophilic complex with high first-pass extraction fraction and deposition and retention in the brain in proportion to cerebral blood flow (perfusion). {07}{09}{10}{11}{19}{25}{28} Its radionuclide emissions permit external imaging of the cerebral distribution of the agent, thus allowing the detection of altered regional cerebral perfusion. The retention in the brain of technetium Tc 99m bicisate results from in vivo metabolism (deesterification) of the primary complex to polar, less diffusable compounds (mono- and di-acids). {01}{07}{10}{18}{25}{28}Distribution:

High initial cerebral uptake with rapid blood clearance after intravenous injection (less than 10% of the administered activity remains in the blood after 5 minutes) {09}{12}{15}{19}{25}. Approximately 5 to 8% of administered activity localizes in the brain within 5 minutes after injection and exhibits little change for one hour after injection. Brain washout is approximately 20% between 5 and 60 minutes after injection and approximately 10% per hour thereafter. {09}{10}{11}{15}{19}{25}{26}{28}Time to radioactivity visualization:

* For adults; intravenous injection. Data based on information from the Oak Ridge Associated Universities, Radiopharmaceutical Internal Dose Information Center. {05}† Calculated according to the method of the International Commission on Radiological Protection (ICRP) publication 60. {05}Elimination:
Renal—About 50% of the administered activity is excreted as metabolites within 2 hours, and about 74% within 24 hours. {01}{11}{18}{19}{28}
Fecal—About 12% of the administered activity is excreted after 48 hours. {01}{28}

Pregnancy—
Tc 99m (as free pertechnetate) crosses the placenta. Although studies have not been done with technetium Tc 99m bicisate in humans, the estimated absorbed radiation dose to the uterus is 6.99 mGy/1110 MBq (0.69 rad/30 mCi) for a 2-hour void, and 12.2 mGy/1110 MBq (1.23 rad/30 mCi) for a 4.8-hour void. There is no evidence demonstrating embryonic or fetal harm at these doses. {05}

Nevertheless, the possibility of pregnancy should be assessed in women of child-bearing potential. In these situations, the physician should use discretion and reduce the administered activity of the radiopharmaceutical to the lowest possible amount. {02}

Although it is not known whether technetium Tc 99m bicisate is distributed into breast milk, it is known that Tc 99m as free pertechnetate is distributed into breast milk. Based on the assumption that the Tc 99m in breast milk is in the form of pertechnetate, and based on the effective half-life of the radionuclide in breast milk, the daily volume of milk, a dose factor relating the radionuclide to its critical organ (thyroid) in the nursing infant, and the maximum permissible dose to that organ, a guideline has been proposed. According to this guideline, it has been calculated that nursing can be safely resumed when the concentration in breast milk reaches 30.3 × 10 -4 megabecquerels (8.2 × 10 -2 microcuries) per mL. This level of activity is probably reached, in the majority of patients, within 24 hours after administration of 740 megabecquerels (20 millicuries) of technetium Tc 99m–labeled radiopharmaceuticals. {04}Pediatrics

There have been no specific studies evaluating the safety and efficacy of technetium Tc 99m bicisate in pediatric patients. However, no pediatrics-specific problems have been documented to date. {01}

Geriatrics

Diagnostic studies performed to date using technetium Tc 99m bicisate have not demonstrated geriatrics-specific problems that would limit the usefulness of technetium Tc 99m bicisate in the elderly. {01}{07}{14}{22}{24}{25}Medical considerations/Contraindications
The medical considerations/contraindications included have been selected on the basis of their potential clinical significance (reasons given in parentheses where appropriate)— not necessarily inclusive (» = major clinical significance).

Risk-benefit should be considered when the following medical problem exists
Sensitivity to the radiopharmaceutical preparation

Side/Adverse Effects
The following side/adverse effects have been selected on the basis of their potential clinical significance (possible signs and symptoms in parentheses where appropriate)—not necessarily inclusive:Those indicating need for medical attentionIncidence rareAngina{01}(chest pain)difficulty breathing{01}hallucinations{01}hypertension{01}seizures{01}skin rash{01}

Those indicating need for medical attention only if they continue or are bothersomeIncidence rareAgitation or anxiety{01}{05}dizziness{01}drowsiness{01}headache{01}nausea{01}{05}parosomia (transient, mild, pleasant aromatic odor){01}{05}

Patient Consultation
As an aid to patient consultation, refer to Advice for the Patient, Radiopharmaceuticals (Diagnostic).

In providing consultation, consider emphasizing the following selected information (» = major clinical significance):Description of use
Action in the body: Concentration of radioactive bicisate in brain

Retention of radioactivity in brain allows visualization

Small amount of radioactivity used in diagnosis; radiation received is low and considered safeBefore having this test» Conditions affecting use, especially:Sensitivity to the radiopharmaceutical preparation

Breast-feeding—Not known if technetium Tc 99m bicisate is distributed into breast milk, but Tc 99m as free pertechnetate is distributed into breast milk; temporary discontinuation of nursing may be recommended to avoid any unnecessary absorbed radiation dose to the infantPreparation for this test
Special preparatory instructions may be given; patient should inquire in advancePrecautions after having this test
Adequate intake of fluids before and after administration of technetium Tc 99m bicisate; voiding frequently for 2 to 6 hours after administration to promote urine flow and to minimize absorbed radiation dose to bladder

General Dosing Information
Radiopharmaceuticals are to be administered only by or under the supervision of physicians who have had extensive training in the safe use and handling of radioactive materials and who are authorized by the Nuclear Regulatory Commission (NRC) or the appropriate Agreement State agency, if required, or, outside the U.S., the appropriate authority.

Adequate hydration of the patient is recommended before and after administration of technetium Tc 99m bicisate to promote urinary flow and blood pool clearance. Also, urination is recommended as often as possible for 2 to 6 hours after the examination to promote urine flow, thereby minimizing absorbed radiation dose to the bladder. {01}Safety considerations for handling this radiopharmaceutical
Improper handling of this radiopharmaceutical may cause radioactive contamination. Guidelines for handling radioactive material have been prepared by scientific, professional, state, federal, and international bodies and are available to the specially qualified and authorized users who have access to radiopharmaceuticals. {03}

Note: Prior to labeling, kit can be stored between 15 and 25 °C (59 and 77 °F). {01}{05}

Preparation of dosage form:
To prepare injection, an oxidant-free sodium pertechnetate Tc 99m solution is used. See manufacturer's package insert for instructions. {01}Stability:
Technetium Tc 99m bicisate is stable at room temperature for a period of at least 8 hours after reconstitution. {06} However, the manufacturer's package insert recommends that the product be used within 6 hours after preparation. {01}{28}Incompatibilities:
If oxidants such as peroxides and hypochlorites are present in the sodium pertechnetate Tc 99m used for labeling, the final preparation may be adversely affected and should be discarded. {01}Note: Caution—Radioactive material.

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